Tokyo -LRB- CNN -RRB- -- Engineers will need six to nine months to bring the damaged nuclear reactors at the Fukushima Daiichi power plant to heel , the plant 's owners said Sunday in their first public timetable for ending the crisis .

It will take three months to reduce the levels of radioactivity in the plant and restore normal cooling systems in the reactors and spent fuel pools , the Tokyo Electric Power Company announced . Another three to six months will be needed before the reactors are fully shut down and new shells are built around their damaged housings , the company said .

Meanwhile , Japan 's government said it would try to decontaminate `` the widest possible area '' in that period before deciding whether the tens of thousands who have been forced to flee their homes will be allowed to return , said Goshi Hosono , an adviser to Japanese Prime Minister Naoto Kan. .

`` We have to go step by step in order to resolve the problems one by one , '' Hosono said .

The timetable was released five days after Kan called for Tokyo Electric to show Japanese a pathway to ending the worst nuclear accident since the 1986 Chernobyl disaster . A day earlier , the company would not comment on an industry group 's estimate that restoring normal cooling would take two to three months -- a period comparable to the first stage of Sunday 's plan .

Tokyo Electric spokesman Hiro Hasegawa acknowledged that public pressure helped speed the company 's decision to release a plan and warned that the outline remained tentative -- `` but we will do our best '' to stick to it , he said .

Because of the still-unknown volume of highly irradiated water flooding the basements of units 1-3 , where the cooling equipment is normally housed , the utility is working toward building a separate cooling system . That system would remove heat from the water being pumped through the reactors and decontaminate it before circulating it back through them .

Currently , engineers have improvised by pumping roughly 170 metric tons -LRB- 45,000 gallons -RRB- of water a day into each reactor , an unknown portion of which is leaking out . The leaking water comes out full of such particles as radioactive iodine and cesium , the byproducts of the reactors .

At the plant on Sunday , workers used remote-controlled robots to record radiation , water and temperature data in the building that houses reactor No. 3 . Photos released by the utility showed the devices , provided by the U.S. company iRobot , opening the inner door to the reactor and entering the darkened building .

`` Everything is a high-radiation area inside the reactor buildings , '' Hasegawa told reporters at a briefing for international news outlets -- another first for a company that has been sharply criticized for its handling of the crisis .

Meanwhile , Tokyo Electric Chairman Tsunehisa Katsumata fended off nearly a dozen questions from Japanese reporters about whether he or other top executives planned to resign as a result of the disaster .

`` At this point , we do not have any decisions or discussions about resigning , as all our efforts is towards resolving the situation , '' Katsumata said . `` We are not sure if resigning is the best way to take the responsibility or to stay in position to resolve the situation . '' Any decisions may wait until the company 's general shareholders meeting in June , he said .

The 5-week-old crisis began March 11 , when the plant was swamped by the tsunami that followed northern Japan 's historic earthquake . The 14 - to 15-meter -LRB- 45 - to 48-foot -RRB- wave knocked out the plant 's coolant systems , causing the three reactors operating at the time to overheat .

The results included two spectacular explosions that blew apart the housings of the No. 1 and No. 3 reactors and the release of a massive amount of radioactivity that has shrunk considerably , but continued Sunday .

The wild card in the utility 's plan may be reactor No. 2 , where another suspected buildup of hydrogen is believed to have ruptured the suppression pool -- a doughnut-shaped reservoir at the base of the reactor . That may make it more difficult to carry out one of the first stages of their planned cooling process , filling the concrete primary containment shell around the reactor pressure vessel with water , Hasegawa said .

Unless that damage is repaired somehow , that part of the plan may be unsuccessful , he said .

Tokyo Electric also plans to build a new structure to support the No. 4 unit 's spent nuclear fuel pool , around which fires -- the cause of which has yet to be determined -- severely damaged a nearby building .

Hosono said there is no indication this pool is compromised or leaking highly radioactive water or fumes , calling the planned structure a protective measure given concerns about considerable damage to the main No. 4 nuclear reactor building .

Japan 's government declared Fukushima Daiichi a top-scale nuclear disaster last week , warning residents of several towns outside the current 30-kilometer -LRB- 19-mile -RRB- danger zone around the plant to evacuate or prepare to leave their homes . Chief Cabinet Secretary Yukio Edano visited the stricken area Sunday , including a brief trip into the 20-kilometer radius from which all residents have been ordered out .

Clad in a white protective suit and face mask , Edano got within about 15 kilometers of the plant as he met with police who are still searching the area for victims of the March disaster .

`` Ensuring people 's livelihoods and security is our foremost priority , '' Edano said after meeting with the governor of Fukushima Prefecture , Yuhei Sato .

Radiation levels in the area are not high enough to cause immediate health effects , but prolonged exposure could cause an increased risk of cancer , according to government data and reports from outside researchers . In Iitate , a village Edano visited Sunday , government figures released Sunday show cumulative doses of radiation since the accident are already more than half the 20-millisievert limit the government

set for long-term evacuations .

Iitate is about 40 kilometers northwest of the plant , outside the danger zones drawn in the early days of the crisis . Hosono said the government does not yet know how much of the contaminated areas can be cleaned up , but added , `` We will try to decontaminate as much of an area as possible . ''

Workers stopped a severe leak of contaminated water into the Pacific Ocean on April 6 , but elevated levels of the short-lived nuclear waste iodine-131 recorded over the weekend could indicate a new problem , a Japanese safety official announced Saturday . Iodine concentrations sampled Saturday around the No. 2 water intake were 6,000 times Japan 's legal standards , up from 1,100 times on Thursday and down slightly from Friday 's figure of 6,500 times .

That number is far below the levels recorded when the earlier leak was spewing radioactive iodine into the ocean at 7.5 million times the limit . Authorities have built a silt and placed steel plates around the intake fence to corral the contamination since April 6 .

Iodine-131 has a radioactive half-life of eight days , and the increase could be either from a fresh leak or from sediment stirred up while placing steel panels around the intakes , said Hidehiko Nishiyama , the top spokesman for Japan 's Nuclear and Industrial Safety Agency .

`` They will continue to monitor this carefully , '' Nishiyama said . `` At this point , they have not visually found any leakage of any water into the ocean , and it is hard to check the conditions around -LRB- reactor -RRB- No. 2 due to high radiation levels . ''

Susan Olson , Hiroo Saso , Yuki Arakawa , Asuka Murao and CNN 's Junko Ogura contributed to this report for CNN .

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NEW : Tokyo Electric plans a new structure to support the No. 4 unit 's spent nuclear fuel pool

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Robots probe darkened reactor No. 3

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Radiation readings in one town are halfway to the government 's evacuation threshold

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Tokyo Electric says it will take 6 to 9 months to wind down the nuclear crisis